Overview of common SQL languages (DDL, DML, DQL)

As we all know, SQL (Structure Query Language) is the core language of the database, the recent period of time to learn the database, some of the basic concept is a bit ambiguous, today simply put these common SQL concepts simple record to make a distinction.

Classification:

• DDL: Data Definition language (CREATE, DROP, ALTER)

• DML: Data Manipulation language (INSERT, DELETE, UPDATE)

• DCL: Data Control Language (GRANT, REVOKE)

• DQL: Data Query Language (SELECT)

Overview:

1. DDL (data definition Language): definition language

DDL mainly includes: Create, DROP, ALTER, mainly used to create various objects in the database: tables, views, indexes, synonyms and so on;

such as CREATE TABLE, create VIEW, DROP TABLE, and so on.

2. DML (Data Manipulation Language): Manipulation language

DML contains additions and deletions to the data in the table: INSERT, DELETE, UPDATE,DML language is mainly the data in the database operation, affecting the specific data records.

3. DCL (Data Control Language): Language

When it comes to control, it is naturally inseparable from authority, so the function of the DCL language is to grant (grant) and reclaim (REVOKE) permissions;

4. DQL (data query Language): Querying language

DQL, also known as "data retrieval statement", extracts the required information from the data, and the select is most frequently used;

Command format: SELECT < field name > from < table name > WHERE < condition >

Overview of common SQL languages (DDL, DML, DQL)